Marketing channels are sets of interdependent organizations participating in the process of making a product or service available for use or consumption. They are the set of pathways a product or service follows after production, culminating in purchase and consumption by the final end user. Some intermediaries — such as wholesalers and retailers — buy, take title to, and resell the merchandise; they are called merchants. Others — brokers, manufacturers' representatives, sales agents — search for customers and may negotiate on the producer's behalf but do not take title to the goods; they are called agents. Still others — transportation companies, independent warehouses, banks, advertising agencies — assist in the distribution process but neither take title to goods nor negotiate purchases or sales; they are called facilitators(促进者).